This invention relates to laser marking systems of the type which are widely used to mark various industrial parts with information such as part numbers, lot numbers, manufacturers' names, etc. Such marking systems typically fall into two categories; namely, focused spot systems and mask systems.
In a focused spot system, e.g., a commercially available Lumonics LightWriter product, a laser beam (typically a YAG or Continuous Wave CO.sub.2 beam) is steered toward a part (i.e., work surface) through a focusing optic by computer controlled x and y galvanometer mounted mirrors. The focusing optic establishes the laser spot diameter for power density, working clearance (focal length and depth of focus), and marking field (work area). Computer control of the mirror movement enables adjustment of character style, size, shape, writing speed and location in the marking field. For metal marking and most other non-transparent marking applications, a YAG laser is generally used. In its Q-switched mode, a focused spot laser can produce several thousand watts of peak power for engraving hard material such as steel. For many transparent materials and other non-metal marking applications, a CW CO.sub.2 laser provides an alternative to YAG focused spot marking.
In a mask system, e.g., a commercially available Lumonics LaserMark product, an interchangeable copper mask or "light stencil" containing the information to be marked is placed in the laser beam path. A TEA CO.sub.2 is typically used to provide enough pulse energy to selectively remove or alter a thin layer of material on the work surface. Using mirrors, the laser beam is directed through the mask and a focusing optic. The focusing optic concentrates laser energy to an effective level for marking. In this manner, a complete message can be "fired" onto the workpiece in a single pulse having a duration on the order of one microsecond. Mask marking systems are most commonly used for non-metal marking applications requiring very high throughput with infrequent code changes.
Such commercially available laser marking systems are typically used with a conveyor which serially delivers parts to a marking station where they are sequentially marked one part at a time.
The present invention is directed to a system for increasing marking throughput by splitting a primary laser beam into multiple secondary laser beams for simultaneously marking multiple workpieces.
U.S. Patents directed to beam splitting optical systems include U.S. Pat. Nos. 3,617,702; 3,763,441; 3,767,310; 4,257,673; 4,670,639; 4,970,369; 5,003,550; 5,089,903; 5,112,121; 5,115,444; 5,136,424; 5,166,818; and 5,177,750.